*2.1. CPHSS-Based Tool Materials*

The object of the study was composite powder high speed steels (CPHSSs), the components of which have a powder composition according to the chemical composition corresponding to the widespread industrial high speed HS6-5-2C steel (AISI M2 according to ISO 4957 [76]) with the addition of 20% refractory compounds TiC, TiCN, and Al2O3. CPHSS occupies an intermediate position between the classic tool materials such as high speed steels (HSSs) and carbide alloys in their properties. The introduction of refractory carbides, carbonitrides, and oxides into the CPHSS composition provides them with high

hardness and heat resistance and the high speed powder base with high viscosity and ductility. CPHSS can be classified as a generic class of adaptive tool materials [77–80].

The industrial technology of hot isostatic pressing of powder compositions followed by pressure treatment by heated blank extrusion was used to obtain experimental samples (Figure 3). Sixteen samples of each tool material were tested. All experiments were repeated five times to obtain data. The following variants of samples of tool materials based on HSS with and without additives of refractory compounds were studied:


Preliminary studies carried out at MSTU "STANKIN" showed that an increase in the content of refractory compounds over 20% significantly reduces the strength characteristics of the material [47,49]. The research was limited to the specified content of alloying additives since it was focused on the process of interrupting cutting (milling) when the risk of brittle fracture of the tool material increases.

Different values of the fundamental physical and mechanical properties characterized the samples prepared for research, precontrolled in the laboratories of the university (Table 1).


**Table 1.** Physical and mechanical properties of research samples.
